Something that we discovered from balloon flying and low-level helicopter aerial work is, as I think was mentioned earlier horses, cattle, pigs are relatively happy if they can SEE what's making the noise.
Trouble is, these animals are not wired to look UP for danger having never had an airborne enemy.
If you surprise these animals, say by flying low over a field bounded by high trees, they go bonkers - usually trying to go straight through the fence or up the nearest tree.
We conducted several experiments so that we could operate with the least disturbance to these animals. The first was a herd of young cattle, the helicopter, with G/A radio contact approached the field from some distance fairly flat and I stood in the herd "talking to" the girls (well, not IN the herd but near enough to get away if it went pear-shaped). They were fine, couldn't care less.
The second time was with a group of Highland cattle. They were lying down doing what cows do. We did the same flat bomber command approach and landed 50 yards from them. They didn't even get up. Horses seem to act in a similar way if they can see what's going on. I can't guarantee that this will work all the time, but it was interesting.
As I say, if you surprise them and they can't see what's going on - all hell can break loose.
There was a video made by a farmer/balloonist about 10 years ago aimed at sport and GA flyers to get them to understand the issues, don't know if it's still available. I will try to find out.